As an important realization form of the energy Internet, the integrated energy system enhances energy utilization efficiency through multienergy complementation and market mechanisms. However, it introduces more risk at the same time. To ensure the safety of the integrated energy system, the importance of establishing a risk assessment system for the integrated energy system has become increasingly important. This paper identifies and explores the risk factors in the integrated energy system, divides the risks into three categories: risks in planning, dispatch and operation. A comprehensive risk evaluation index system is established. Furthermore, the corresponding preventive measures or countermeasures are proposed for each type of risk to improve the resistance of the integrated energy system to various risks. Finally, in the case studies, the harm grade caused by different type of risk to further control the risk based on the risk assessment is evaluated and the effectiveness of the results are verified. It is found that the proposed method improves the risk management level.